Continuous process for oxidation of alkyl benzenes



July 31, 1962 R. E. PENNINGTON 3,047,613

CONTINUOUS PROCESS FOR OXIDATION OF ALNYI. BENzENEs Filed March 29, 1960 INVENTOR. ROBERT E. PENNINGTON,

fir,

ATTORNEY.

United States Patent O 3,047,613 CONTINUOUS PROCESS FOR OXIDATION OF ALKYL BENZENES Robert E. Pennington, Baytown, Tex., assignor, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, NJ., a corporation of Delaware Filed Mar. 29, 1960, Ser. No. 18,406 7 Claims. (Cl. 260--475) This invention relates to an improved method for conducting a continuous process lfor the production of carboalkoxy benzenes by the liquid phase catalytic oxidation of an alkyl benzene with molecular oxygen in the presence of methanol.

Briefly, the present invention is directed to an improved method for conducting a process for the liquid phase catalytic oxidation of an alkyl benzene with molecular oxygen in the presence of methanol in a reaction zone wherein the fresh alkyl benzene Kfeed stock is added to the condensate from the o gas from. the reactor, wherein the thus-formed mixture is resolved into an alkyl benzene condensate phase containing said lfresh alkyl benzene and an aqueous phase, and wherein said alkyl benzene condensate phase is recycled to the reaction zone.

When an alkyl benzene is oxidized with molecular oxygen (e.g., puried molecular oxygen, air, or molecular oxygen diluted with an inert gas such as carbon dioxide) in the presence of methanol, a wide variety of reaction products are formed including alkyl benzene conversion products, methanol oxidation products `and substantial quantities of by-product water of reaction.

It is necessary to remove at least a major portion of the water that is formed during the reaction so that the reaction mixture will contain not more than about weight percent of -water and this is conveniently accomplished by conducting the reaction at a temperature which is near the boiling point of Water for the pressure employed. However, volatilization of the water will also result in volatilization of other components of the reaction mixture to a significant extent whereby unreacted methanol, methanol oxidation products, unreacted alkyl benzene and alkyl benzene conversion products are vaporized and leave the reaction zone together with the volatilized water and o gas components (c g., nitrogen, carbon monoxide, car-bon dioxide, etc.). Because of the comparatively large quantity of unreacted or partially reacted material present in the vapor, it is desirable to process this vapor for the recovery of valuable components thereof.

It has been discovered, in accordance with the present invention, however, that this presents serious problems, particularly where recycle type operations are employed, because of the comparatively high concentration of alkyl benzene conversion products that are present in the vapor.

The concentration of alkyl benzene conversion products in the vapor 'will be particularly large when the reaction temperature for the liquid phase reaction is high or the methanol concentration in the liquid phase is high, or both, so as to maximize the rate of esteriiication of the aromatic acids formed by the oxidation reactions. Thus, for example, when the temperature, pressure, and methanol feed rate `are correlated so as to provide from about 5 to l5 weight percent of liquid methanol in the liquid phase, the condensable components of the vapor that are withdrawn from the reactor will constain cornparatively large amounts of methanol, unreacted alkyl benzene and, most signioantly, alkyl benzene conversion products.

When the vapor from the reaction zone is cooled to a temperature suiiicient to liquefy the condensable components thereof, the thus-obtained condensate will comprise a mixture of water, methanol, methanol oxidation ice products, alkyl benzene and alkyl benzene conversion products. It might ordinarily be expected that the methanol, methanol oxidation products and water would separate from the alkyl benzene and alkyl benzene conversion products in order to provide a heavy aqueous phase which could be separated from the alkyl benzene condensate phase by any suitable phase separation technique such as gravity settling. However, the presence of large quantities of methanol in the aqueous phase tends to decrease the specific gravity of the aqueous phase, whereas the concentration of alkyl benzene conversion products in the alkyl benzene phase tends to increase the specific gravity of the alkyl benzene condensate phase. Thus, the normal specic gravity differential that exists with respect to water `and oil will tend to be minimized with respect to the condensate and, as a conseqence, even under the most favorable conditions, the driving force for phase separation (i.e., the difference between the specific gravity of the oil phase and the water phase) 'will be significantly reduced whereby long settling times will be required. Moreover, even a moderate increase in the concentration of the alkyl benzene conversion products inthe alkyl benzene condensate phase will actually cause the normal specific gravity dijerential to be reversed and the alkyl benzene condensate phase will become heavier than the aqueous phase. This will result in phase inversion. In an intermediate situation, concentrations of the various components present may be such that the condensate will comprise a single phase containing both the alkyl benzene and water components in contrast to the separate water and oil phases that would normally be expected or else the water phase and oil phase will have approximately equal specc gravities and will not separate. Still further, the changes in composition required to bring about the above-noted changes in the speciiic gravity relationship are slight so that even minor changes in the composition of the condensate will result in major changes in the settling rates observed thereof. As a consequence, unless special precautions are taken, it will not be possible to obtain dependable phase separation of the condensate with a supernatant alkyl benzene condensate phase during continuous operations.

Phase separation may be obtained in dependable fashion by adding water t-o the condensate in significant quantities (e.g., by adding from about 5 to 50 weight percent of water based on the total weight of the condensate or, on a different basis, about 15 to 100 weight percent of water based on the weight of the aqueous phase). Selective removal of heavyalkyl benzene conversion products is frequently necessary. While this is an eh'ectve method, it poses an economic debit upon the process since it is necessary to provide a separate cooler and a separate accumulator for selective-condensation and removal of the alkyl benzene conversion products.

In accordance with the present invention, an improved method of operation is provided which will result in satisfactory phase separation in a normal manner even in the presence of large quantities `of heavy xylene conversion products without the need for selective removal thereof.

Preferably, in accordance with the present invention, a condensate that is derived from the vapor withdrawn from a reaction zone wherein an alkyl benzene is catalytically oxidized in liquid phase with molecular oxygen in the presence of methanol, is treated for dependable phase separation and for recovery of the unreacted alkyl benzene and alkyl benzene conversion products for recycle by simultaneously adding water and at least a portion of the fresh alkyl benzene feed stock for the process to the condensate prior to attempting phase separation thereof. This provides a two-fold advantage. Thus, a convenient method for `fresh feed stock addition is provided and,

moreover, the fresh alkyl benzene feed stock when added to the process in this fashion insures smooth and satisfactory operation of the process by insuring dependable phase separation into an upper condensate alkyl benzene recycle fraction and an aqueous fraction with only minimized equipment requirements.

The alkyl benzene feed stock to be used in accordance with the present invention is an alkyl benzene containing one or a plurality of C1 to C4 alkyl groups attached directly to the benzene ring, the alkyl benzene containing oxygenated contaminants. By way of example, the starting materials may comprise methyl benzenes such as toluene, xylenes, trimethyl benzenes, tetramethyl benzenes, a pentamethyl benzene or hexamethyl 'benzene or a corresponding ethyl, n-propyl, isopropyl, butyl, or isobutyl benzene. Polyalkyl benzenes `containing a plurality of alkyl groups of varying chain lengths may also be utilized such as, for example, a cymene, l-methyl-3- butyl benzene, l-methyl-4-tertiary-butyl benzene, etc. A single isomer, a plurality of isomers or a plurality of alkyl benzenes of different molecular weight may be utilized.

The alcohol feed material is methanol.

The preferred starting materials are the methyl benzenes and methanol, because less oxygen is required, because less by-product water is formed and because workup of the reaction mixture is simplified.

The oxidizingr medium to be employed is molecular oxygen and a preferred oxygen charge stream is air. However, it is within the scope of the present invention to utilize purified molecular oxygen or molecular oxygen diluted with another inert gas such as carbon dioxide.

The catalyst that is used is a salt of a polyvalent heavy metal which is soluble in the liquid reaction mixture as exemplified by the salts (e.g., the naphthenates, acetates, bromides, etc.) of cobalt and manganese, etc. The `catalyst concentration should preferably be within the range from about l to about 10,000 p.p.m. of polyvalent heavy metal based on the total weight of the reaction mixture. Catalyst promoters are optionally employed and, more particularly, soluble bromine salts such as cobalt bromide, ammonium bromide, manganese bromide, etc. or hydrobromic acid are employed because of their high promotional activity, both with respect to the oxidation reaction and with respect to the esterification reaction that are involved.

The term recycle type operation as used in this application means a continuous operation wherein products of the conversion operation (both liquid and vapor) are continually processed exteriorly of the reaction zone for the removal of nonreactive components of the reaction mixture and wherein unreacted alcohol, unreacted alkyl benzenes and alkyl benzene conversion products ar'ereturned to the reaction zone.

The term alkyl Ibenzene conversion products as used herein is intended to Ainclude aromatic type products formed in the reaction zone including reaction products of the alkyl |benzene with oxygen only as well as reaction products (such as oxidation-esterication reaction products) of alkyl benzene, oxygen, and methanol. A'lso, since the alkyl benzene will ordinarily contain small quantities of aromatic type impurities, the term alkyl benzene conversion products is also intended to include conversion products of the aromatic impurities. Accordingly, for 'the purpose of this application, the term alkyl benzene conversion products is defined as the aromatic conversion products of the alkyl benzene feed stock and aromatic impurities contained therein and comprising aromatic alcohols, aromatic aldehydes, aromatic acids, methyl esters of aromatic acids, partial methyl esters of polybasic aromatic acids, etc.

rIhe term methanol oxidation products as used herein means reaction products of methanol and oxygen including formaldehyde, formic acid, methyl formate and methylal,

Unreactive components of the reaction mixture may be dened as those components of the reaction mixture which are not ultimately reactive with oxygen or methanol, or both, to give a desired carbomethoxy product.

The invention will be further illustrated with respect to the accompanying drawing which is a schematic ow sheet illustrating a preferred embodiment of the present invention.

Turning now to the drawing, there is shown a reaction zone l@ provided with charge lines 12, 14, and 16 containing pumps 13, 15, and `17, respectively, for the methanol, air, and an alkyl benzene, respectively. A suitable catalyst for the process such as cobalt naphthenate may be added as required by charge line 18 controlled by a valve 20.

Within the reaction zone 10 the xylene is catalytically oxidized with molecular oxygen under suitable operating conditions (eg, a temperature within the range of 350 to 550 F., a pressure within the range of about 500 to 1000 p.s.i.g. and an average residence time within the range of about 0.2 to 2 hours), all of which are correlated with the rate at which alkyl benzene type materials, methanol, and molecular oxygen are charged to the reaction zone l0 in order to maintain free methanol in the liquid phase. More specifically, the conditions are correlated to maintain l to l `weight percent of methanol in the liquid phase. Under these conditions, from about l to 5 weight percent of water will also normally be present in the liquid phase.

Vapor product is withdrawn from the reactor by way of a vapor line 22 and a portion of the liquid phase is continually withdrawn by way of a liquid draw-off line 24.

The Vapor in the vapor line 2.12 is charged to a cooler 48 wherein condensable components are liquefied and is then charged by way of a line 50 to an accumulator 52 wherein the condensate is collected. Tail gas such as nitrogen, carbon dioxide, and carbon monoxide may be vented from the accumulator S2 by way of a vent line 57. The condensate is discharged from the accumulator 52 by way of a bottoms draw-off line 54- containing a Ipressure reducing valve S3 and `a pump 56; line Sileading to a manifold 58. Water is added to the manifold by way of a water charge line containing a pump 63 and controlled by a valve 62. For example, from about 5 to 25 weight percent of water (based on the weight of the condensate) may be added by way of line 60.

In accordance with this embodiment of the present invention, fresh alkyl benzene from any suitable source (not shown) is charged by Way of an alkyl benzene charge line 64 containing a pump 66 to a manifold 68 and from thence by -way of a line to the manifold 5S. Suitably, from about 5 to 25 weight percent of fresh alkyl benzene (based on the weight of the condensate) is added by line 70.

The resultant mixture of fresh alkyl benzene, fresh water, and condensate is discharged from manifold 58 by way of a line 72 leading to separator 74 wherein phase separation is accomplished in order to provide a heavy aqueous phase and a supernatant alkyl benzene phase comprising fresh and unreacted alkyl benzene and alkyl benzene conversion products. The aqueous phase is discharged from the separator 74 by way of a bottoms discharge line 76 for further processing in any desired manner. For example, the aqueous fraction 76 may be charged to a distillation zone (not shown) and separated into a heavy water fraction, a light methanol oxidation products fraction composed of methylal, methyl formate, and methanol and an intermediate methanol fraction for recycle to reaction zone l0.

The alkyl benzene condensate phase from the separator 74 is taken overhead by way of a recycle line 7S leading to a mainfold 80 which in turn leads to the charge line lo for the alkyl benzene.

Although the reaction product 2d may be processed in any desired manner for the recovery of a carbomethoxy benzene product, the first step in the carbomethoxy recovery process is preferably a flash step wherein water, methanol, methanol oxidation products, alkyl benzene and some of the alkyl 'benzene conversion products are flashed or otherwise removed from the liquid phase in order to provide a heavy carbomethoxy benzene concentrate. This may be conveniently accomplished, for example, by charging the liquidstream 24 to a pressure reduction valve 26 having a discharge line 28 leading to a fractionation zone 30 wherein the separation of the liquid product stream intoa heavy oxidate fraction and a vapor fraction is accomplished.

The concentrated carbomethoxy benzene fraction (heavy oxidate) is discharged from fractionation zone 30 by way of a discharge line 33 for `further processing (e.g., by fractional crystallization or distillation, or both) in order to recover the carbomethoxy benzene and an alfkyl benzene conversion products `fraction for recycle. l The vapor from the fractionation zone 30 is discharged by way of a line 32 controlled by a valve 34. The vapor fraction 32 may be recycled directly to the reaction Zone I10. This may be done, for example, through the provision of a recycle line 40 controlled -by valves 41 and 42 and containing condenser 44 and a pump 46. In this situation, therefore, the valve 34 is closed and the valves 41 and 42 are opened whereby the Vapor fraction 32 is charged to the condenser 44 `for condensation and whereby any resultant liquid may be pressured to reaction pressure by the pump 46 and then returned to the reaction zone 10. Alternately, all or part of the condensate from cooler 44 may be charged to the vapor condensate system for simultaneous processing therewith (e.g., by way 'ofa branch line 43 controlled by a valve 45). In this event, valve 41 is closed.

Y If it is desired to separately process the vapor fraction 32 from the fractionation zone 30, the valve 42 is closed and the Valve 34 is opened whereby the vapor is charged to a cooler 82 wherein it is condensed. The condensed material comprises Water, methanol, methanol oxidation products, unreacted alkyl benzene and alkyl benzene conversion products and is discharged 'from cooler 82 by way of line 84 containing a pump 83; line 84 leading to a manifold 86. Water is also added as described above rto manifold 86 by a line 88 containing a pump 89 and controlled by a valve 90. In addition, the valve 94 in a branch line 92 interconnecting alkyl benzene manifold 68 with the manifold 86 is opened in order that a portion of the fresh alkyl benzene may be charged by way of the line 92 to the manifold 86 while another portion yof the xylene is being simultaneously charged to the manifold 58 by Way of line 70.

The mixture of condensate, fresh water, and fresh alkyl benzene is discharged from manifold 86 by way of line 96 'leading to a separator 98 wherein the liquid is separated by gravity settling into a supernatant alkyl benzene condensate phase which is withdrawn from separator 98 by Way of a line 100 leading to manifold 80 and a water phase which is discharged by way of a line 102 for further processing (e.g., for the distillation of methanol therefrom for recycle).

It is not to lbe inferred from the foregoing that the only suitable point of addition of the fresh alkyl benzene is intermediate the accumulator 52 and the separator 74. Thus, for example, the alkyl benzene may be added by `appropriate charge lines (not shown) to the vent line 22 through the line 50 from cooler 48, the accumulator 52 or, for that matter, even the separator 74. This will likewise be the situation with respect to the vapor drawotf line 32 from zone 30 in that alkyl benzene may be radded by appropriate lines (not shown) to the vapor line 32, cooler discharge line 84 or even the separator 98. It is Within the scope of the present invention to add the fresh alkyl ybenzene simultaneously at a multiplicity of points as above described through the use of suitable fmanifolding arrangements.

As an example of operation, a continuous process is initiated by charging fresh alkyl benzene to the system through alkyl benzene charge line 64, manifold 68, line 70, manifold 58, line 72, separator 74, line 78, manifold 80, and alkyl benzene charge line 16. A suitable catalyst such as cobalt naphthenate is added to the alkyl benzene by way of the catalyst charge line 18. Air is charged to the reactor by way of the line 14 in order to pressure the reaction zone 10 to the desired pressure (e.g., 700 p.s.i.g.), and oxidation of the alkyl benzene is initiated. After the reaction is initiated, methanol is added by Way of a charge line 12. The air, alkyl benzene and methanol charge rates are interrelated so that 0.4 part of air and about 0.4 part of methanol are added `for each part of xylene type materials added by Way of line 16. Under these conditions, the temperature in the reaction zone may suitably be about 475 F.

As a result of the reaction, vapor will be formed which is continuously withdrawn by way of line 22 and liquid may be Withdrawn by way of line 24. The composition of the vapor and the composition of the liquid are set forth in Table lI.

TABLE I Product Compositions Liquid Product, Wt

Vapor Product, Wt

Percent Component Percent 1Formaldehyde, formic acid, methylal, methyl formate. t Ip-tTolyl alcohol, p-to1yl aldehyde, p-toluic acid, p-methyl o ua e.

3p,p'-Bitolyl, pto1y1-ptoluate and acids and esters formed from p-Xylene impurities and catalyst decomposition products.

The liquid fraction 24 is separated in yfractionation zone 30 into a heavy oxidate fraction and a light vapor fraction which is removed by way of lines 32 and 43 to a r line 54.

The heavy oxidate fraction is withdrawin from fractionation zone 30 by way of line 33 for further processing for the recovery of dimethyl terephthalate as the product and for the recovery of a xylenes recycle fraction comprising unreacted p-xylene and p-xylene conversion products -which is recycled to the reaction zone 10 by a suitable recycle line (not shown).

The vapors in the line 22 are passed to cooler 48 where they are cooled to about F. in order to recover condensable components. The material is discharged to 'line 50 from cooler 48 into accumulator 52 wherein off gas is removed by vent line 57. The condensate is removed by line 54 and charged to manifold 58 wherein it is mixed with about 25 weight percent of water and about 8.5 percent of fresh alkyl benzene charged in the above described manner. The resultant mixture is charged from line 72 to separator 74 wherein phase separation occurs.

When the process is first started up, the xylene type materials in the condensate will consist essentially of pxylene. However, as Arecycle operations progress, progressively larger and larger amounts of xylene conversion products will be present in the condensate until, under described reaction conditions, the xylene conversion products will comprise about 20 weight percent of the total condensate. No problem is encountered with respect to the separation of the condensate into an aqueous phase and an oil phase.

To illustrate the problems that are encountered in processing condensate from the off gas in a manner other than that described in this application, continue operations as described above but add water only. Although phase separation occurs, the specic gravity of the aqueous phase withdrawn by way of line 76 is only 0.92 while the specific gravity of the xylene condensate fraction withdrawn by line 78 is 0.89. Thus, the specific gravity differential is only 0.03. When the temperature within the reaction zone is raised to about 500 F., increased volatilization of the xylene conversion products occurs and, particularly, increased volatilization of the most harmful heavy part of the xyrle-ne conversion products (methyl toluate, monoethyl terephthalate and dimethyl terephthalate) `occurs whereby the specific gravity differential between the aqueous phase 76 and the xylene condensate phase 78 becomes even less. After about 6 hours of operation in a representative run, the differential had become so small that separation of the phases by gravity separation did not occur in the separator 74. Thus, visual observation of a sample of material obtain-ed under these conditions showed the presence of two phases which did not separate. Separation did not occur even when the sample was allowed to stand for'8 hours.

However, when both about weight percent of fresh water and about 10 weight percent of fresh xylene were added to the condensate by way of lines 60 and 70, respectively, the specific gravity differential between the aqueous phase and the xylenes condensate phase was increased and good separation was again obtained.

Having described the invention, what is claimed is:

v1. In a continuous method for Vthe production of a carbomethoxy benzene by the catalytic liquid phase reaction of an alkyl benzene having from l to 4 carbon atoms per alkyl substituent with methanol and oxygen in a reaction zone under oxidation-esterication conditions, wherein a vapor product is continuously withdrawn from said reaction zone and cooled to form a condensate stream, and a liquid product is withdrawn from said zone, ashed and cooled to produce a vapor fraction stream, the improvement which comprises adding to at least one of said streams both a water stream amounting to about 5% to about 50% of the weight of said stream and an alkyl benzene stream amounting to about 5% to about 25% of the weight of said stream, whereby said stream separates into an aqueous and a supernatant alkyl benzene phase, withdrawing said aqueous phase, and recycling said alkyl benzene phase to said reaction zone.

2. A method in accordance with claim 1 wherein said water and alkyl benzeneare added to the condensate stream.

3. In a continuous method for the production of a carbomethoxy benzene by the catalytic liquid phase oxidation of a methyl benzene in a reaction zone with molecular oxygen in the presence of methanol wherein fresh methyl benzene is continuously charged to said reaction, wherein reaction products including a vapor product and a liquid product are continuously withdrawn from said reaction zone, said vapor product and said liquid product comprising water of reaction, unreacted methanol, methanol oxidation products, unreacted methyl benzene and methyl benzene conversion products, wherein alkyl benzene conversion products are recovered, and wherein said liquid product is flashed and cooled to form a vapor fraction stream, the improvement which comprises continuously mixing water and fresh methyl benzene with at least one of said streams, charging said rnixture to a separator for gravity separation of said mixture into a water phase and a supernatant methyl benzene phase, and continuously recycling said methyl benzene phase to said reaction zone, the water being added to said stream amounting to between 5% and 50% by weight of said stream, and the alkyl benzene added to said stream amounting to between about 5% and about 25% 0f said stream.

4. In a continuous method for the production of a dimethyl phthalate by the catalytic liquid phase oxidation of a xylene in a reaction zone with molecular oxygen in the presence of methanol wherein fresh xylene is continuously charged to said reaction, wherein the reaction products include a vapor product stream and a liquid product, wherein said liquid product is flashed and cooled to produce a vapor fraction stream, said vapor product stream and said vapor fraction stream comprising a mixture of water of reaction, unreacted methanol, methanol oxidation products, unreacted methyl xylene and xylene conversion products, and wherein dimethyl phthalate conversion products are recovered, the improvement which comprises continuously mixing water and fresh methyl benzene with one of said streams, about 5 to 50 weight percent of water and about 5 to 25 weight percent of fresh xylene, based on the weight of said stream, being mixed therewith, charging said mixture to a separator for gravity separation of said mixture into a Water phase and a supernatant methyl benzene phase, and continuously recycling said methyl benzene phase to said reaction zone.

5. In a method for the continuous production of dimethyl terephthalate which comprises the steps of continuously catalytically oxidizing paraxylene in a reaction zone in liquid phase with molecular oxygen in the presence of `methanol whereby a liquid phase reaction mixture is formed containing methanol, methanol oxidation products, p-xylene, p-xylene conversion products and water, continuously removing a liquid product stream from said reaction zone, continuously separating said liquid product stream into a liquid heavy oxidate fraction and a vapor fraction containing water, methanol, methanol oxidation products, p-xylene and p-xylene conversion products, continuously condensing said vapor fraction to provide a first condensate, continuously withdrawing from said reaction zone an off gas containing condensable components including water, methanol, methanol oxidation products, pxylene and p-xylene oxidation products, continuously liquefying said condensable components of said off gas to provide a second condensate, the improvement which comprises continuously adding said rst and second condensates, Water and fresh alkyl benzene to a separator for resolution into a water phase comprising Water, methanol and methanol oxidation products and a supernatant phase comprising p-xylene and p-xylene conversion products and recycling said supernatant phase to said reaction zone, from about 5 to about 50 weight percent of water and from about 5 to about 25 weight percent of fresh p-xylene being added to said separator, based on the total weight of said rst and second condensates.

6. A method as in claim 5 wherein dimethyl terephthalate is recovered from said heavy oxidate and the remainder of said heavy oxidate is recycled to said reaction zone and wherein methanol is recovered from said water phase and recycled to said reaction zone.

7. In a method of continuously carrying out the oxidation-esterication reaction of an alkyl benzene with methanol to produce a carboalkoxy benzene product which comprises contacting said alkyl benzene and said methanol with oxygen in a reaction zone under oxidation-esterification conditions, continuously withdrawing a liquid product from said zone, separating said liquid product into a vaporous fraction containing methanol, methanol conversion products, alkyl benzene, and a portion of the alkyl benzene oxidation products, and a liquid heavy oxidate fraction, recovering said carboalkoxy benzene from said heavy oxidate fraction, continuously withdrawing a vaporous product from said zone, the improvement which comprises introducing said vaporous product and said vaporous fraction with fresh water and fresh alkyl benzene into a liquid phase settler to form a supernatant alkyl benzene phase and an aqueous phase, withdrawing said super- 9 10 natant alkyl benzene phase and recycling said alkyl ben- 2,825,738 Ellendt et al. Mar. 4, 1958 zene phase to said reaction zone. 2,879,289 Johnson Mar. 24, 1959 References Cited in the le of this patent OTHER REFERENCES UNITED STATES PATENTS 5 Lange: Handbook of Chemistry, 9th ed., pages 518- 2,so2,859 Feuerly Aug, 13, 1957 19 and 718-19 (1956)' 

1. IN A CONTINUOUS METHOD FOR THE PRODUCTION OF A CARBOMETHOXY BENZENE BY THE CATALYTIC LIQUID PHASE REACTION OF AN ALKYL BENZENE HAVING FROM 1 TO 4 CARBON ATOMS PER ALKYL SUBSTITUTENT WITH METHANOL AND OXYGEN IN A REACTION ZONE UNDER OXIDATION-ESTERIFICATION CONDITIONS, WHEREIN A VAPOR PRODUCT IS CONTINUOUSLY WITHDRAWN FROM SAID REACTION ZONE AND COOLED TO FORM A CONDENSATE STREAM, AND A LIQUID PRODUCT IS WITHDRAWN FROM SAID ZONE, FLASHED AND COOLED TO PRODUCE A VAPOR FRACTION STREAM, THE IMPROVEMENT WHICH COMPRISES ADDING TO AT LEAST ONE OF SAID STREAM BOTH A WATER STREAM AMOUNTING TO ABOUT 5% TO ABOUT 50% OF THE WEIGHT OF SAID STREAM AND AN ALKYL BENZENE STREAM AMOUNTING TO ABOUT 5% TO ABOUT 25% OF THE WEIGHT OF SAID STREAM, WHEREBY SAID STREAM SEPARATES INTO AN AQUEOUS AND A SUPERNATANT ALKYL BENZENE PHASE, WITHDRAWING SAID AQUEOUS PHASE, AND RECYCLING SAID ALKYL BENZENE PHASE TO SAID REACTION ZONE. 